class Solution {
public:
    int uniquePaths(int m, int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        vector<vector<int>> dp(m, vector<int>(n, 0));
        for (int i = 0; i < m; i++)
            dp[i][0] = 1;
        for (int j = 0; j < n; j++)
            dp[0][j] = 1;
        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++) 
                dp[i][j] = dp[i-1][j] + dp[i][j-1];
        }
        return dp[m-1][n-1];
    }
};